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Harry Vereecken - One of the best experts on this subject based on the ideXlab platform.
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particle size distribution models their characteristics and fitting capability
Journal of Hydrology, 2015Co-Authors: Hossein Bayat, Mostafa Rastgo, Moharram Mansouri Zadeh, Harry VereeckenAbstract:Summary Many attempts have been made to characterize particle size distribution (PSD) curves using different mathematical models, which are primarily used as a basis for estimating Soil hydraulic properties. The principle step in using Soil PSD to predict Soil hydraulic properties is determining an accurate and continuous curve for PSD. So far, the characteristics of the PSD models, their fitting accuracy, and the effects of their parameters on the shape and position of PSD curves have not been investigated. In this study all developed PSD models, their characteristics, behavior of their parameters, and their fitting capability to the UNSODA database Soil samples were investigated. Results showed that beerkan estimation of Soil transfer (BEST), two and three parameter Weibull, Rosin and Rammler (1 and 2), unimodal and bimodal Fredlund, and van Genuchten models were flexible over the entire range of Soil PSD. Correspondingly, the BEST, two and three parameter Weibull, Rosin and Rammler (1 and 2), hyperbolic and offset renormalized log-normal models possessed a high fitting capability over the entire range of PSD. The few parameters of the BEST, Rosin and Rammler (1 and 2), and two parameter Weibull models provides ease of use in Soil Physics and mechanics research. Thus, they are seemingly fit with acceptable accuracy in predicting the PSD curve. Although the fractal models have physical and mathematical basis, they do not have the adequate flexibility to contribute a description of the PSD curve. Different aspects of the PSD models should be considered in selecting a model to describe a Soil PSD.
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kirkham s legacy and contemporary challenges in Soil Physics research
Soil Science Society of America Journal, 2011Co-Authors: William A Jury, Harry Vereecken, J W Hopmans, Ya A Pachepsky, L R Ahuja, B E Clothier, Keith L Bristow, G J Kluitenberg, Per Moldrup, Jirka SimůnekAbstract:Don Kirkham was instrumental in transforming Soil Physics into a modern scientific discipline by developing theories based on verifiable hypotheses, creating methods to test the hypotheses, and applying the theories to problems of importance to society. We, the recipients of the Don and Betty Kirkham Award in Soil Physics, show how this legacy continues to affect Soil Physics. We describe eight longstanding or emerging research areas in Soil Physics that contain key unsolved problems. All are field oriented, with applications to a number of important issues in agriculture and the environment. The first three problems deal with the topic of characterization of field-scale Soil water properties, within which we describe progress on scaling, effective hydraulic properties, and the relationship between Soil structure and function. We then move to the description of unstable flow and characterizing water repellency, and finish with discussions on the effect of plants on transport processes, characterizing Soil microbial diversity, and the importance of Soil ecological infrastructure in providing ecosystem services. The challenges we discuss reflect inherent gaps between the complexity of the Soil environment and its biogeochemical function, and the limited measurement and analytical tools at our disposal. Improving our predictive capabilities at relevant spatial and temporal scales will be necessary to address some of the long-standing problems within agriculture and the Soil environment.
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determination of Soil hydraulic properties using magnetic resonance techniques and classical Soil Physics measurements
MAGNETIC RESONANCE IN POROUS MEDIA: Proceedings of the 10th International Bologna Conference on Magnetic Resonance in Porous Media (MRPM10) including , 2011Co-Authors: Laura Stingaciu, Lutz Weihermuller, Andreas Pohlmeier, Siegfried Stapf, Harry VereeckenAbstract:Water and solute movement as any other transport processes through Soil are influenced by the hydraulic properties of the Soils. The heterogeneities of the Soils imply heterogeneous spatial distribution of the hydraulic properties leading to heterogeneous distribution of Soil water content. This may affects the water availability for plant growth, the groundwater contamination and nutrients losses within the root zone. The measurement techniques available today for the estimation of Soil hydraulic parameters do not account for the heterogeneity of the sample and treat each measurement sample as a homogeneous representative volume. On the other side natural Soils contain large heterogeneities mostly in terms of inclusions of different materials. Therefore the purpose of this study is to estimate Soil hydraulic properties of a heterogeneous sample by combining classical multi‐step‐outflow (MSO) with magnetic resonance imaging (MRI) experiments. MSO experiments were performed on a sample filled with sand and sand‐clay mixture in a coaxial structure. During each pressure application MRI images at 4.7 T (200 MHz) were recorded using a pure phase‐encoding MRI sequence in order to provide information about the Soil water content at specific locations within the coaxial sample. The recorded cumulative outflow and water content data were used as input data in the inversion of the MSO experiment. For the simulation and inversion of the MSO experiment we used the hydrological model HYDRUS‐2D3D in which the initial hydraulic parameters of the two materials were estimated based on CPMG‐T2 relaxation measurements on homogeneous sub‐samples. The results show conclusively that the combination of the two MRI and MSO methods leads to a unique estimation of the hydraulic properties of two materials simultaneously.
Peter A C Raats - One of the best experts on this subject based on the ideXlab platform.
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the contributions of lewis fry richardson to drainage theory Soil Physics and the Soil plant atmosphere continuum
Frontiers in Environmental Science, 2018Co-Authors: Peter A C Raats, J H KnightAbstract:Lewis Fry Richardson (1881-1953) was an English polymath, who made important contributions to many fields, including numerical weather prediction, finite difference solutions of partial differential equations, turbulent flow and diffusion, fractals, and the cause and evolution of conflicts. In 1922 he published the book `Weather Prediction by Numerical Process'. He did the research for this book under difficult circumstances just before, during, and just after World War I. The book received a lot of attention initially, but methods like those proposed in it were not successfully implemented until the invention of fast digital computers around 1950. To model heat and mass transfer in the atmosphere, Richardson did much original work on turbulent flow and defined what is now known as the Richardson number. His technique for improving the convergence of a finite difference calculation is known as Richardson extrapolation, and was used by John Philip in his 1957 semi-analytical solution of the Richards equation for water movement in unsaturated Soil. With the first draft of his book just finished, from mid-1916 the pacifist Richardson drove an ambulance in France during the later part of World War I. But even then, In his spare time, he did weather related experiments and computations, rewrote the first draft of his book, and started a new scientific career in the study of conflicts, again using existing and inventing new mathematical tools. Posthumously, most of Richardson$'$s contributions in various fields received considerable attention. But important exceptions are his contributions to Soil science and hydrology, on which we focus in this paper. His first published papers in 1908 concerned the numerical solution of the free surface problem of unconfined flow of water in saturated Soil, arising in the design of required ditch spacing for draining peat. He developed and used a graphical method to solve this problem. This and other practical problems stimulated his interest in numerical methods and soon led him to the challenge of numerical weather prediction. Richardson formulated an elaborate model for transport processes in the atmosphere. For the lower boundary of his atmospheric model he needed to understand the movement of liquid
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milestones in Soil Physics
Soil Science, 2006Co-Authors: Peter A C Raats, Martinus Th Van GenuchtenAbstract:This special issue of Soil Science celebrates the enormous accomplishments made during the past century or more in the field of Soil science, including some of the key articles published in Soil Science during its 90 years of existence. In this article, we focus on the contributions in Soil Physics, exemplified by the articles of Willard Gardner (1919) and John Philip (1957c), both of which are reprinted in this issue. Much of the overview is limited to the Physics of water flow in unsaturated Soils as described with the Richards equation, including its mathematical solutions. (Soil Science 2006;171:S21‐S28)
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developments in Soil water Physics since the mid 1960s
Geoderma, 2001Co-Authors: Peter A C RaatsAbstract:Abstract The theory for movement of water in unsaturated Soils published by Richards 70 years ago is still an important starting point for the analysis of most Soil physical problems. Over the last quarter century, the interest in finding new solutions of the Richards equation by either analytical or numerical methods was intense, particularly with regard to field situations. Experimental methods became more diverse and sophisticated: electromagnetic methods for measuring water content and salinity are now reliable and widely available, inverse methods for inferring the Soil physical properties have matured. But during this period, we see also a widening of the scope of Soil Physics beyond the classical theory of Richards with further studies of various multiphase aspects—particularly, simultaneous movement of water and air, simultaneous transport of heat and moisture, flow of water and transport of solutes in structured Soils—, of water movement in Soils subject to swelling and shrinkage, and of transport of solutes in unsaturated Soils. The latter two subjects became manageable by replacing the traditional spatial descriptions by material descriptions in which, respectively, the solid phase serves as the reference continuum for the water and the water serves as the reference continuum for the solutes. Progress was driven not only by a healthy theoretical, computational, and experimental basis, but also by productive interaction with adjoining disciplines and by challenging societal problems.
K. Reichardt - One of the best experts on this subject based on the ideXlab platform.
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Representative Gamma-ray Computed Tomography Calibration for Applications in Soil Physics
Brazilian Journal of Physics, 2011Co-Authors: L. F. Pires, R. C. J. Arthur, O. O. S. Bacchi, K. ReichardtAbstract:Tomographic image quality in Soil Physics applications is extremely dependent on calibration. Here, good calibrations of the system are necessary to avoid errors during Soil evaluations by computed tomography (CT), which can hamper interpretations of physical parameters of the Soil. In order to analyze the relevance of a good calibration curve (CC) for measurements of Soil physical properties, determinations of Soil bulk density ( ρ _ b ) were obtained using four different CCs established for a homemade CT scanner dedicated especially to Soil Physics. The calibrations of the system were obtained through the relationship between tomographic units and corresponding linear attenuation coefficients ( μ _1) of different materials. Data show that different calibration curves produce distinct ρ _ b values affecting the quality of results of this Soil physical property when evaluated by CT. However, it was demonstrated that even using non-homogeneous materials for CT calibration the results of ρ _ b practically are of the same order of magnitude of the whole system error estimated in 0.05 g cm^ − 3 (taking the water as reference).
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twenty five years of computed tomography in Soil Physics a literature review of the brazilian contribution
Soil & Tillage Research, 2010Co-Authors: L. F. Pires, O. O. S. Bacchi, Jaqueline A R Borges, K. ReichardtAbstract:The last 25 years of the use of computed tomography in Brazil, applied to Soil Physics is here presented. This period ranges from the first publication made by Brazilian researchers in 1985 to 2010. Discussion is made on the use of 1st to 3rd generation tomographic systems, with millimetric and micrometric resolutions, using X and gamma-ray, and neutron sources. The main achievements of these researchers involve studies on Soil compaction, surface Soil sealing, effects of wetting-drying cycles on Soil structure, Soil porosity and pore size distribution, water movement through Soils and effects of agricultural management systems on Soil structure. Therefore, the results presented in this review have the aim of giving to the reader the state of art of the Brazilian research using tomographic systems.
Orme Bethany - One of the best experts on this subject based on the ideXlab platform.
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Slippery liquid‐infused porous surfaces: The effect of oil on the water repellence of hydrophobic and superhydrophobic Soils
'Wiley', 2021Co-Authors: Mccerery Rebecca, Woodward John, Mchale Glen, Winter Kate, Armstrong Steven, Orme BethanyAbstract:Soil wettability is important for understanding a wide range of earth system processes, from agricultural productivity to debris flows and sediment fan formation. However, there is limited research considering how Soil–water interactions, where the Soil grains are naturally hydrophobic, might change in the presence of oil from natural hydrocarbon leakage or oil spills. Here we show how slippery liquid‐infused porous surfaces (SLIPS) apply to hydrophobic Soils, by physical modelling of surfaces of different grain sizes and examining their interactions with water before and after impregnation with silicone oil. Using contact and sliding angle measurements and laser scanning fluorescence confocal microscopy, we demonstrate that Soil SLIPS can be created with thick oil layers and thin conformal oil layers on median grain sizes of 231 μm and 32 μm, respectively. Until now, SLIPS have only been observed in human‐made materials and biological surfaces. The mechanisms reported here demonstrate that SLIPS can occur in natural granular materials, providing a new mechanism for water‐shedding in Soil and sediment systems. Furthermore, the water‐shedding properties may be long lasting as conformal oil layers are stabilized by capillary forces. These results have important implications for understanding Soil Physics and mechanics where oil is present in a Soil, and for agricultural hydrophobicity on shallow slopes
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Slippery liquid-infused porous surfaces: The effect of oil on the water repellence of hydrophobic and superhydrophobic Soils
'Wiley', 2020Co-Authors: Mccerery Rebecca, Woodward John, Mchale Glen, Winter Kate, Armstrong Steven, Orme BethanyAbstract:Soil wettability is important for understanding a wide range of earth system processes, from agricultural productivity to debris flows and sediment fan formation. However, there is limited research considering how Soil–water interactions, where the Soil grains are naturally hydrophobic, might change in the presence of oil from natural hydrocarbon leakage or oil spills. Here we show how slippery liquid‐infused porous surfaces (SLIPS) apply to hydrophobic Soils, by physical modelling of surfaces of different grain sizes and examining their interactions with water before and after impregnation with silicone oil. Using contact and sliding angle measurements and laser scanning fluorescence confocal microscopy, we demonstrate that Soil SLIPS can be created with thick oil layers and thin conformal oil layers on median grain sizes of 231 μm and 32 μm, respectively. Until now, SLIPS have only been observed in human‐made materials and biological surfaces. The mechanisms reported here demonstrate that SLIPS can occur in natural granular materials, providing a new mechanism for water‐shedding in Soil and sediment systems. Furthermore, the water‐shedding properties may be long lasting as conformal oil layers are stabilized by capillary forces. These results have important implications for understanding Soil Physics and mechanics where oil is present in a Soil, and for agricultural hydrophobicity on shallow slopes
Nicholas Jarvis - One of the best experts on this subject based on the ideXlab platform.
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upscaling Soil saturated hydraulic conductivity from pore throat characteristics
Advances in Water Resources, 2017Co-Authors: Behzad Ghanbarian, Allen G. Hunt, Todd H. Skaggs, Nicholas JarvisAbstract:Abstract Upscaling and/or estimating saturated hydraulic conductivity K sat at the core scale from microscopic/macroscopic Soil characteristics has been actively under investigation in the hydrology and Soil Physics communities for several decades. Numerous models have been developed based on different approaches, such as the bundle of capillary tubes model, pedotransfer functions, etc. In this study, we apply concepts from critical path analysis, an upscaling technique first developed in the Physics literature, to estimate saturated hydraulic conductivity at the core scale from microscopic pore throat characteristics reflected in capillary pressure data. With this new model, we find K sat estimations to be within a factor of 3 of the average measured saturated hydraulic conductivities reported by Rawls et al. (1982) for the eleven USDA Soil texture classes.